The technical solution involves the design of a triggering circuit of overvoltage protection with an asymmetric element representing the area of electrical protection devices designed to restrict overvoltage in a protected distribution network. The overvoltage protection comprises a spark gap connected to input terminal I and input terminal II, whereas a triggering circuit of the overvoltage protection device with an asymmetric element, featuring an asymmetric three-pole arrester, is connected the spark gap in three poles.
Known technical designs of modern lightning arrestors come with an efficient spark gap, equipped with a triggering circuit that quickly actuates the spark gap if impulse overvoltage occurs. Due to its design, the spark gap deactivates quickly, i.e. the flowing follow-on-current is interrupted once the transient overvoltage from the impulse overvoltage has finished. A variety of triggering circuit designs that shall actuate a discharge between main electrode I and main electrode II of the spark gap using an auxiliary electrode contain a transformer. The main drawback of known designs of triggering circuits with a transformer is that the size of the current flowing between the auxiliary electrode and main electrode I or main electrode II of the spark gap is considerably limited by the impedance of the transformer secondary winding, which extends the time necessary to trigger the spark gap; eventually, the transformer secondary winding can be destroyed by thermal overloading due to the limited cross-section of the transformer secondary winding wires, and consequently, the overvoltage protection device loses its functionality, which then endangers the protected equipment by impulse overvoltage.
An example of such a design is document U.S. Pat. No. 6,111,740 “Overvoltage protection system and overvoltage protection element for an overvoltage protection system”, where the overvoltage protection device system features a spark gap with two main electrodes and at least one auxiliary electrode connected to the output of the trigger voltage of the triggering circuit. The triggering circuit has a triggering capacitor, ignition triggering element and a transformer that features primary and secondary winding. The output from the secondary winding represents an ignition voltage output from the triggering circuit. The disadvantage of such a design is the secondary winding's high impedance, which limns the current flowing through the auxiliary electrode and one of the main electrodes. Such overloading can result in damage to the triggering circuit and loss of functionality of the overvoltage protection device. Consequently, in the design published in document DE19914313 “Overvoltage protection system for e.g. protecting electronic equipment against transient overvoltages caused by lightning discharge, provides monitoring equipment for ignition circuits with thermal and/or dynamic overload switching off”, the ignition circuit is extended with security elements and signaling of the operating condition.
Another known triggering circuit design for overvoltage protection, which forms a constituent part of document FR2902579 “Electrical installation protection device i.e. surge suppressor, has a triggering unit passing spark gaps from the blocking state, in which gaps oppose the current circulation, to the passing state, in which the gaps permit the fault current to flow in branches”, deals with the synchronous triggering of two overvoltage elements connected in series, where the overvoltage elements consist of spark gaps, whereas the triggering circuit contains two secondary windings. In this design, the above-stated deficiencies are even greater.
Document U.S. Pat. No. 4,683,514 “Surge voltage protective circuit arrangements” shows an arrangement where a protective resistor is situated between the auxiliary electrode of a spark gap and a transformer secondary winding. The protective resistor partially protects the winding from damaging, at the same time, however, it limits the current, i.e. the triggering ability of the triggering circuit as well, and, at the same time, the arch stability is limited.
Similarly, the design of the triggering circuit of the overvoltage protection as indicated in document US2003007303 “Pressure-resistant encapsulated air-gap arrangement for the draining off of damaging perturbances due to overvoltages” represents only a basic circuit solution. The disadvantage of the secondary winding's high impedance of the transformer persists.
Document CZ25171 “Design of the triggering circuit of overvoltage protection” represents merely an improved circuit design with the persisting disadvantage of secondary windings high impedance.
According to an aspect of the invention, a triggering circuit of the overvoltage protection is provided with an asymmetric element specified for actuating a spark gap either in a symmetric or asymmetric arrangement of main electrode I, connected to input terminal I, main electrode II, connected to input terminal II, and an auxiliary electrode; where the principle of the design features main electrode I of the spark gap connected through a thermo-sensitive disconnector, and also through a parallel combination of varistor II and capacitor I to electrode I of an asymmetric three-pole lightning arrester, whose middle electrode is connected via the transformer primary winding to main electrode II of the spark gap, whose auxiliary electrode is connected via varistor I to electrode II of the asymmetric three-pole lightning arrester, connected to main electrode II of the spark gap via the transformer secondary winding, whereas the thermo-sensitive disconnector is coupled via a thermal coupling with varistor II and, at the same time, the voltage at the asymmetric three-pole lightning, arrester features static ignition voltage U1 between electrode II and the middle electrode is higher than static ignition voltage U2 between the middle electrode and electrode I.
The overvoltage protection comprises a spark gap that features main electrode I, main electrode II and an auxiliary electrode to facilitate easier breakdown between main electrode I and main electrode II, which is enabled by the design of the triggering, circuit of the overvoltage protection with an asymmetric element.
The advantage of such a design of a triggering circuit of overvoltage protection according to an aspect of the invention lies in increased reliability of the triggering, respectively, actuating capability of the triggering circuit due to the used asymmetric element, consisting of or comprising an asymmetric three-pole arrester.
The modified design of the triggering circuit of the overvoltage protection with the asymmetric element mentioned above consists of or comprises condenser II interconnected between the junction connecting electrode I of the asymmetric three-pole lightning arrester with varistor II and capacitor I, and between main electrode II of the spark gap.
Another design according to an aspect of the invention of the triggering circuit of overvoltage protection with an asymmetric element, specified for actuating the spark gap either in a symmetric or asymmetric arrangement of main electrode I, connected to input terminal I, main electrode II, connected to input terminal II, and an auxiliary electrode, comprises spark gap main electrode I, which is connected via a thermo-sensitive disconnector and varistor II to electrode I of the asymmetric three-pole lightning arrester, whose middle electrode is connected via a transformer primary winding to main electrode II of the spark gap, whose auxiliary electrode is connected via varistor I to electrode II of the asymmetric three-pole lightning arrester, connected via the transformer secondary winding to main electrode II of the spark gap, whereas one end of the series combination of resistor and capacitor I is connected to the junction connecting the thermo-sensitive disconnector with varistor II, and its other end is connected to main electrode II of the spark gap, and the thermo-sensitive disconnector is coupled with the thermal coupling with varistor II and, at the same time, the voltage at the asymmetric three-pole lightning arrester is as follows: static ignition voltage U1 between electrode II and the middle electrode is higher than static ignition voltage U2 between the middle electrode and electrode I.
Another possible design according to an aspect of the invention of the triggering circuit of overvoltage protection with an asymmetric element, specified for actuating the spark gap either in a symmetric or asymmetric arrangement of main electrode I, connected to input terminal I, main electrode II, connected to input terminal II and an auxiliary electrode, comprises main electrode I of the spark gap connected via a thermo-sensitive disconnector, and also via a parallel combination of varistor II and capacitor I, to one pole of the voltage dependent triggering element, whose second pole is connected via the transformer primary winding connected to main electrode II of the spark gap, whose auxiliary electrode is connected via varistor I to electrode I of the asymmetric three-pole lightning arrester, which is connected to its middle electrode via varistor III, and the middle electrode is connected via the transformer secondary winding to main electrode II of the spark gap, which is connected to electrode II of the asymmetric three-pole lightning arrester, whereas the thermo-sensitive disconnector is coupled with a thermal coupling with varistor II and, at the same time, the voltage at the asymmetric three-pole lightning arrester is as follows: static ignition voltage U1 between electrode II and middle electrode is higher than static ignition voltage U2 between the middle electrode and electrode I.
The modified above-mentioned design of the triggering circuit of overvoltage protection with an asymmetric element comprises capacitor II interconnected between the junction connecting the voltage-dependent triggering element to varistor II and capacitor I, and between main electrode II of the spark gap.
The last design according to an aspect of the invention of the triggering circuit of overvoltage protection with an asymmetric element specified for actuating the spark gap either in symmetric or asymmetric arrangement of main electrode I, which is connected to input terminal I of main electrode II, connected to input terminal II, and an auxiliary electrode, comprises main electrode I of the spark gap connected via a thermo-sensitive disconnector and varistor II to one pole of the voltage-dependent triggering element, the second pole of which is connected to main electrode II of the spark gap via the transformer primary winding, whereas the auxiliary electrode of the spark gap is connected via varistor I to electrode I of the asymmetric three-pole lightning arrester, and this is connected via varistor III connected with its middle electrode, which is connected via the transformer secondary winding to main electrode II of the spark gap, which is connected to electrode ii of the asymmetric three-pole lightning arrester, whereas one end of the series combination of the resistor and capacitor I is connected to the junction connecting the thermo-sensitive disconnector to varistor II, and its other end is connected to main electrode II of the spark gap, whereas the thermo-sensitive disconnector is coupled with a thermal coupling with varistor II and, at the same time, voltage at the asymmetric three-pole lightning arrester is as follows: static ignition voltage U1 between electrode II and the middle electrode is higher than static ignition voltage U2 between the middle electrode and electrode I.
The designs of the triggering circuit of overvoltage protection with asymmetric element which feature a voltage-dependent triggering element, which beneficially comprises a two-pole arrester or a two-pole electronic circuit based on power triggering semiconductors.